Currently 2G (GSM), 2.5G (GPRS) and 3G (UMTS/UTRA) mobile or cellular telecommunications networks (PLMNs) co-exist. A development of the radio access network part of 3G mobile telecommunications is “evolved” UTRA or E-UTRA, also referred to as LTE (Long Term Evolution). “System Architecture Evolution” (SAE) is the development of the core network part of 3G mobile telecommunications. The combined core network and radio network development is sometimes referred to as SAE/LTE. It is desirable for mobile terminals to provide continuous service also when moving from an LTE coverage area to a 3G or 2G coverage area.
With current GPRS/UMTS packet switched (PS) networks, the GGSN is selected when the PDP context is activated. This is described in 3GPP TS 23.060, which is fully incorporated herein by reference, see particularly Annex A: APN and GGSN Selection.
The PLMN operator may configure the network to select a GGSN that is close to where the mobile device is when a PDP context is activated. However, if a subscriber keeps their mobile device switched on and moves a large physical distance, sub-optimal routing of data traffic can occur.
A corresponding problem also exists for SAE/LTE networks in relation to Packet Data Network Gateway (PDN-GW) selection.